Bourne Archive: Muspratt: Grinding malt

The Bourne Archive

Muspratt’s Chemistry, Theoretical, Practical & Analytical (ca. 1859)

Extracts Concerning Beer, 5: Grinding Malt.

The web pages intended to be linked from this introduction are from an article on brewing, under the heading ‘Beer’. The original article is presented here in several web pages, respectively dealing with: 1, barley; 2, malting; 3, water; 4, hops; 5, grinding: 6, mashing; 7, saccharometry; 8, boiling; 9, cooling; 10, fermentation; 11, cleansing.

Vol. 1. pp. 247-248.

Brewing.—After the foregoing details, the main subject to which they refer will now be entered upon, namely, brewing, and to make the matter as clear and intelligible to the reader as possible, the treatise will be divided into several heads, corresponding with the various sections of the work, as actually performed in the manufactory. These are grinding and mashing; boiling, hopping, and cooling; fermenting, cleansing, fining, and storing; in addition to which, the particular methods for making other kinds of Malt beverages, besides the ales ¹ most generally consumed, will be pointed out and discussed.

It may be mentioned at the outset, that grinding, mashing, and fermenting have been referred to at some length under Alcohol and the manufacture of whisky, at page 58, et seq., and therefore a full explanation of these operations will in some degree be unnecessary ²; but as they are performed in a manner somewhat dissimilar in this case, in conformity with a particular purpose, it will be requisite to notice them as far as they affect the preparation of beer.

GRINDING.—Little, however, need be said on grinding, in addition to what has already been advanced ³; but were any one thing to be particularized more than another, it would be the necessity of having the natural cohesiveness of the grain destroyed in such a way, that the water may have free access to every particle of it, to insure the entire extraction of the valuable constituents. Of the various methods resorted to, whether by reducing the grain between stones in the ordinary way, of by steel mills, wherein it is cut or torn in the same manner as coffee is ground, or by crushing between rollers, that mode is preferable which disintegrates the grain completely, and loosens the husk from the fleshy parts without separating the two. A moment’s consideration will show that these conditions are not fulfilled by either of the first two methods; and it is only from the use of rollers that the malt can be expected to make the nearest approach to the criterion mentioned. A secondary but important advantage is gained, by having the grain completely broken up though still adhering together; namely, the facility with which the mash is racked off, leaving only little of the extract in the grains. When it is ground fine, the matter, besides being apt to set and form a mucilaginous magma, retains much of the liquor, which cannot be removed except by long washing, thus rendering the worts dilute, and exposing them to the danger of acetification in the succeeding treatment. When the particles of the grains still adhere, though their natural texture is broken, each shell forms, as it were, a filter, through which the clear liquor percolates readily, leaving any matter, which might be taken up mechanically, behind. If the grain be torn or sliced, as by metal mills, in which the available matter remains to some extent adhering to the husk in its natural state, considerable loss will be sustained, for the water will not penetrate these parts during the period usually allowed for mashing. That this is the case, is evident from the well-known fact, that dried malt will float on water for a period of twenty-four hours, without absorbing as much of the menstruum as would increase its gravity sufficiently to cause it to sink.

The annexed cuts—Figs. 156, 157—represent, in front and lateral section, the cylinder malt mill. I is a sloping trough, through which the malt passes from its bin or floor to the hopper, A, whence it is shaken between the iron rollers, B, D, working at their extremities in bearers of sockets of hard brass, fitted securely into the side frames, which are also of iron. E is a screw passing through the upright, and serving to force the bearer of one roller towards that of the other, so as to bring them nearer together when the malt is wanted in a finer state of division. G is square end of the axis, by which one of the rollers is turned. The other rotates by means of a pair of equal-toothed wheels, H, fitted to the opposite extremities of the axes of the cylinders. d is a catch working into the teeth of a ratchet wheel, not shown in the engraving, on the end of the rollers. The lever, c, comes in contact with the trough, b, at the bottom of the hopper, giving it a shaking motion, which discharges the malt upon the rollers from the side sluice, a. e e are scraper-plates, the edges of which, pressing on the rollers, remove adhering matter, and thus keep them clean.

When rollers are used they should be of equal size, and move with the same degree of velocity, otherwise the proper and looked-for quality will not be found in the crushed malt. Another important feature is, that the grain ought to be screened or passed through a wire sieve before it falls between the crushers, for the purpose of removing any pebbles, lest they should come against the rollers and injure them. As great inconvenience and loss may be suffered from imperfect grinding, the chief care of the brewer ought to be directed to the erection of such machinery in every department as will efficiently answer all his requirements. After the grinding, the malt is usually conducted by an endless chain of buckets to a proper receptacle placed over the mash-tub, where it remains till required.

Commentary.

1. ^ The distinction between ale and beer is blurred. So far as it goes, ale shows more of the sweetness of the malt and beer, more of the bitterness of the hops. See Beer style.

2. ^ This appears on a separate web page.

3. ^ As footnote 2. The stone grinding process described there is here, said to be unsuited to grinding malt. It was used for grinding grain for animal feed and baking flour.

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